I 



Chemical Papers. 55 



The specific gravity was determined in each case, both as a factor 

 in itself and as a means for converting volume into weight. 



QUANTITATIVE METHODS EMPLOYED. 



Determination of Specific Gravity. — The determinations of 

 specific gravity were made by means of a Geissler's pycnometer, 

 with a capacity of about fifty cubic centimeters, and provided with 

 a delicate thermometer. 



Determination of Tkiosulfate. — In this determination the sul- 

 fides of calcium were removed by means of cadmium. Five cubic 

 centimeters of the dip were stirred into about twenty-five cubic 

 centimeters of freshly boiled distilled water to which had been 

 added a quantity of a five-per-cent. solution of cadmium chloride 

 sufficient to completely precipitate the sulfides. The resulting 

 cadmium sulfide settled at once, was quickly filtered off, and left 

 a clear filtrate. This filtrate was titrated with decinormal iodine 

 solution, using freshly prepared starch as indicator. 



Determination of Calcium. — Twenty-five cubic centimeters of 

 the dip were pipetted into a 250 cubic centimeter measuring flask 

 and diluted to the mark with freshly boiled distilled water ; twenty- 

 five cubic centimeters, representing two and one-half cubic cen- 

 timeters of the original dip, were immediately pipetted out into a 

 beaker; two cubic centimeters of a saturated solution of potassium 

 hydroxide and an excess of bromine water added. The beaker with 

 contents was then placed on a hot plate and digested at just below 

 the boiling-point to the complete oxidation of the sulfur. After 

 cooling, hydrochloric acid was added to acid reaction and the ex- 

 cess of bromine removed by reheating. Ammonia was added to 

 alkalinity and the calcium precipitated by adding a sufficient quan- 

 tity of five-per-cent. ammonium oxalate solution. It was found 

 that less trouble from cloudy filtrates was experienced if this as 

 well as the barium sulfate precipitate spoken of in the next para- 

 graph was allowed to settle for twenty-four or thirty-six hours in a 

 warm place. It was then filtered on an ashless paper filter, ignited 

 to the oxide in a muffle furnace, and immediately weighed. 



Determination of Total Sulfur. — In the determination of total 

 sulfur the same procedure was followed as for calcium up to the 

 point of precipitation, when to the hot acid solution a sufficient 

 quantity of a ten-per-cent. solution of barium chloride was added ; 

 the resulting precipitate of barium sulfate, after standing as men- 

 tioned above, was removed by means of a Gooch filter and filter 

 pump, ignited at low redness, and weighed. 



